Glass-fiber-reinforced plastic products, such as the hull of a boat, a shower stall, a tank, a cowling, or the like, are typically made with known glass fiber which may be that bearing the trademark Fiberglas. These products are generically known as Fiberglas-reinforced parts (FRP) and include at least one layer of glass fibers mixed with synthetic resin to provide rigidity.
In a known glass-fiber-reinforced product, a woven sheet of glass fibers is placed on a gel coated surface and saturated with synthetic resin. After the resin has cured, the product (resin-backed gel coat) is removed from the surface and placed in use. Many times, the product is made with several layers of a glass-fiber-material soaked with resin to produce a thicker, stronger product.
In another method, a formulation of glass fibers, known as Fiberglas chop, is mixed with resin to provide structure for a glass-fiber-reinforced product. This is advantageous since the chop may be sprayed into a mold and mixed with resin during or prior to the spraying of the resin. This process is preferred in many instances since it is much faster than using a layer of woven glass fiber and is thus much less expensive.
A number of glass-fiber-reinforced products include a gel coat as a first layer of the product. Gel coat is a resin-based material which is applied to a mold surface; it gels prior to placing further plastic material in the mold. The gel coat becomes an integral part of the finished laminate; it establishes surface characteristics and appearance. Thus, when using Fiberglas chop, a layer of gel coat is applied to the surface of the mold and Fiberglas chop (mixed with resin) is then sprayed onto the gel coat. This process results in the trapping of air between the layer of gel coat and the first layer of Fiberglas chop. Accordingly, the prior art process requires the step of rolling out the first layer (a thin "skin coat") of Fiberglas chop to remove air bubbles. After the air bubbles have been removed by this rolling out step, a heavy "back-up" layer of Fiberglas chop is ordinarily applied. This step of rolling out takes a substantial amount of time and adds significantly to the cost of the product.
The problem of air voids is explained in "Applications Manual for Cook's Polycor Polyester Resins and Gel Coats", published by Cook Paint and Varnish Company, Kansas City, Mo., Copyright 1978: "It is impossible to remove all air bubbles by contact molding, but their size and distribution is important. Large voids give a whitish appearance when using clear resin.
Since the most critical area is directly behind the gel coat, it is advisable to specify a light cloth or chop for the first layer. Surface pits also must not be predominant."
Another problem of the prior art is known as "black plague." This is a blackening of gel coat caused by combination of cobalt in the gel coat with calcium hypochlorite, for example, contained in water in a spa.